How to fix the error ""openssl" is not an internal or external command, operable program or batch file"?

Question

openvpn

Followed this tutorial .
As a result, I wrote this vars.bat file: https://paste.ubuntu.com/p/VRsfwWBP6x/
Then I opened cmd and wrote: vars
Then: clean-all
Then I wrote: build-dh. This is where the error occurred:
""openssl" is not recognized as an internal or external command, operable program, or batch file"