If you own the myexample.com domain, then your registrar "must" allow you to define the IP addresses of name servers in that domain. Perhaps not through their control panel, you may have to contact them directly.
So you would define
ns1.myexample.com as 18.104.22.168
ns2.myexample.com as 22.214.171.124
for example, then these name servers would be registered in the .com zone. Note that if they do not provide this service, then they are not acting as registrars and so should not be selling domains.
The IP addresses 126.96.36.199 and 188.8.131.52 are the DNS servers that you intend use to for your domain.
So the way it works is someone says "what is the IP address of www.myexample.com". The first question goes to the .com nameservers -> "what are the addresses of the name servers for myexample.com" - the .com nameservers respond, and then the query goes on to the actual name servers to resolve www.myexample.com