Point EC2 instance to subdomain

I have a website landing page http://www.example.com. It's hosted by IONOS, and has my main web landing page and its using WordPress to build it.

I also have an EC2 instance, and I would like my actual app that's running on my EC2 instance at 34.556.24.23:8710, to be found at subdomainapp.example.com

What i'd need you to do, is use Route 53 and The AWS load balancer to point my subdomain (when someone goes on subdomainapp.example.com) to my EC2 instance. Remember for the EC2 public address, it has a port number on the end (8701), so it needs Route 53 and a load balancer.

My main example.com webpage should still be with my current hosting company (IONOS).