Need guide on how to install minidlna to 2.11.157 version

There are multiple guides on how to install minidlna with apt-get.
But as 2.11.157 has busybox there is no apt-get.

Is there any guide on how to install minidlna on MyCloud EX2 2.11.157?

You may want to search in, or post in, the dedicated EX2 subforum where people more familiar with the EX2 and its firmware may be able to assist. This subforum (My Cloud) is generally for the single bay/single drive My Cloud.

https://community.wd.com/c/network-attached-storage/wd-my-cloud-ex2