Creating and organizing Game Menu and Level Menu

I have a game menu which shows different level names. I want level 2-5 to be inactive in the main screen. User can click only on Level 1 button. Onclicking other levels a pop-up will appear.

Level 2 button will be active once level 1 is completed. Level 3 will be active once Level 2 is finished and so on.
I am new to unity and game development. Please help me with this situation.

Thank you for your time…

You will need something like this (unless you want to try to make it yourself):