Problem at changing nameserver

Hello…my problem is …I’m confusing at changing a name server with cloudflare name server, Because
I buy domain at godaddy and hosting at hostgator.
For Merging domain and hhosting…I replaced hosting name server with domain name servers in godaddy(domain)…so now in godaddy has hosting name server…if I I remove that then may be domain and hosting connection will break.

So I’m confusing which nameserver have to replace with cloudflare nameserver

You have to change the nameserver with the registrar, so if you have registered the domain via GoDaddy, that is where you need to update the nameservers.