How to clone an custom object fields to Opportunity object in Salesforce?

Hi,

Write a trigger like this:

trigger CloneOpp on Opportunity (after update){
    
    Custom_Object__c[] ls=new Custom_Object__c[]{};
        for(Opportunity o: trigger.new){
            Custom_Object__c obj=new Custom_Object__c();
            //Assign whichever values you want to clone to the fields of your custom object, for example:
            //obj.name=o.name;
            
            ls.add(obj);
        }
    insert ls;
}

For More look at the Url:- https://developer.salesforce.com/forums/?id=9060G0000005cUUQAY