You have to call the code from the custom button .. i have a similar blog .. refer this link 

Refer this link

https://rajvakati.com/2018/10/17/lightning-component-clone-with-related-records/
https://rajvakati.com/2018/10/17/clone-to-any-sobject-record-with-lightning-component/
 

public class SuperClone {
    private static SuperCloneService service = new SuperCloneService();
    @AuraEnabled
    public static Id doClone(Id parentId) {
        Id clonedId = service.doClone(parentId);
        return clonedId;
    }
}

 

public class SuperCloneService {
    public Id doClone(String parentId) {
        Set<String> querySobject = new Set<String>();
        for(Super_Clone_Objects__mdt m : [select Id, DeveloperName, Label, API_Name__c 
                                          from Super_Clone_Objects__mdt  ]){ 
                                              querySobject.add(m.API_Name__c) ;  
                                          }
        Map <String, Schema.SObjectType> schemaMap = Schema.getGlobalDescribe();
        String objectAPIName = '';
        String keyPrefix = parentId.substring(0,3);
        for( Schema.SObjectType obj : schemaMap.Values() ){
            String prefix = obj.getDescribe().getKeyPrefix();
            if(prefix == keyPrefix){
                objectAPIName = obj.getDescribe().getName();
                break;
            }
        }
        Set <String> fieldMap = schemaMap.get(objectAPIName).getDescribe().fields.getMap().keySet();
        List<String> finalFields = new List<String>() ;
        finalFields.addAll(fieldMap);
        
        SObjectType objToken = Schema.getGlobalDescribe().get(objectAPIName); 
        DescribeSObjectResult objDef = objToken.getDescribe();
        Map<String,String> so = new Map<String,String>();
        Map<String,String> so1 = new Map<String,String>();
        
        for (Schema.ChildRelationship cr: objDef.getChildRelationships()) 
        {
            if(cr.getField().getDescribe().isAccessible()&& cr.getField().getDescribe().isCreateable()&&cr.getField().getDescribe().isAccessible() && cr.getRelationshipName()!=null){
                if(querySobject.contains(''+cr.getChildSObject())){
                    so.put(''+cr.getChildSObject()  , ''+cr.getRelationshipName());
                    so1.put(''+cr.getRelationshipName()  , ''+cr.getField());
                }
            }
        } 
        
        List<String> subqueries = prepareSubqueries(so, schemaMap);
        String query =
            'SELECT ' + String.join(finalFields, ',')+
            ','+String.join(subqueries, ',') +
            ' FROM ' +objectAPIName +
            ' WHERE Id = \''+parentId+'\'';
        
        List<Sobject> parentObj = Database.query(query);
        Sobject parentRecordId = parentObj[0];
        
        Sobject clonedRecord = parentRecordId.clone();
        insert clonedRecord;
        List<sObject> childObjects =cloneChildren(parentRecordId, clonedRecord, so  ,so1);
        insert childObjects;
        System.debug('clonedRecord'+clonedRecord.Id);
        return clonedRecord.Id ;
        
    }
    
    private List<sObject> cloneChildren(
        Sobject parent,
        Sobject child,
        Map<String , String> childRelatedListObjects,
        Map<String , String> childRelatedListObjects1
    ){
        
        List<sObject> childObjects = new List<SObject>();
        for (String childObjectDefinition : childRelatedListObjects.values()) {
            List<sObject> parentRecords = parent.getSObjects(childObjectDefinition);
            System.debug('parentRecords'+parentRecords);
            if (parentRecords != null) {
                List<sObject> records = parentRecords.deepClone();
                System.debug('records'+records);
                for (sObject record : records) {
                    record.put(childRelatedListObjects1.get(childObjectDefinition), child.Id);
                }
                childObjects.addAll(records);
            }
        }
        return childObjects;
    }
    
    private List<String> prepareSubqueries(
        Map<String , String> childrelatedListObjects,
        Map <String, Schema.SObjectType> schemaMap
    ){
        List<String> subqueries = new List<String>();
        for(String childObject : childrelatedListObjects.keySet()){
            List<String> childFields = new List<String>();
            Map <String, Schema.SObjectField> fieldMap = schemaMap.get(childObject).getDescribe().fields.getMap();
            System.debug('fieldMap'+fieldMap);
            for(Schema.SObjectField sof : fieldMap.values()){
                DescribeFieldResult dfr = sof.getDescribe();
                if(dfr.isCreateable()){
                    childFields.add(dfr.getName());
                }
            }
            if(!childFields.isEmpty()){
                String query = '(SELECT ' + String.join(childFields, ',') + ' FROM ' + childrelatedListObjects.get(childObject) + ')';
                subqueries.add(query);
            }
            
        }
        return subqueries;
    }
    
}