How to run a request after each request for a set of requests in a collection?

New to APIs/Postman
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I have solved it as below:

Add below code in Req1 ,
pm.environment.set(“iterationNumber”,1);
postman.setNextRequest(“RunLog _400 body”);

and below code in “RunLog _400 body” request

if (Number(pm.environment.get(“iterationNumber”))==1)
{postman.setNextRequest("Missing type _Code ");}

if (Number(pm.environment.get(“iterationNumber”))==2)
{postman.setNextRequest(“Missing InceptionDa”);}

if (Number(pm.environment.get(“iterationNumber”))==3)
{postman.setNextRequest(“Missing Url _Code 400”);}