How to forward ports on two routers?

Question

Network administration

There is a Huawei HG8240 GPON router, then the Internet goes through the cable to the Upvel UR 825 router.
How to forward ports between these two routers?
I will describe why this is necessary. I use storage from Thecus and I want to use DDNS connection. Thecus itself provides it without problems (through its domains), but you need to forward the ports, but nothing happens. On the Upvel UR 825 ip the storage address is reserved for it.

Answer 1

It is necessary to find NAT in the Huawei settings, enter the IP addresses from where and where and, in fact, the ports themselves. In theory, everything.