How can I convert the control from buttons to ui buttons in unity?

Question

C++ / C#

how I can convert the control from buttons to ui buttons in unity? I find this code with physics which I need and and now I need to redo the control from the `PC to the buttons for the phone
script you can get from the link
https://docs.google.com/document/d/18VshoJIjzIwMSz ...
I don't know where else to post