Reinstalling RTW non-steam version - Install-button is greyed out

[Jakoporeeno]

I've had the mod Roma Surrectum 2 (after installing it for the non-steam version) for a while but haven't played it and I thought I'd install it for the Steam-version, so I follow a video on youtube on how to install RSIII (https://www.youtube.com/watch?v=FNOhyGx2NhQ&t=204s) but in the middle of the video he points out that I need the Alexander-folder in Steam/Steamapps/common which I don't have so I stop trying to install it for the steam-version and attempt to start the game with a shortcut to the old launcher for the non-steam version that I've had for a while - I don't remember exactly what it said on the sign that came up but it said something like it couldn't find the file that it was a shortcut to so I thought that maybe because I installed the steam-version and confused the shortcut destination or something, idk. I decide that I should get a non-steam version of the game to install Roma Surrectum 3 on. I open the first file that needs to be installed and up comes the Rome launcher but the "Install" button is greyed out and I can't install the game, so I think that maybe it's because the game is still on the computer in one sense or another so I go to "Programs and features" in the control panel to find it and uninstall it and I see that I still have Rome - Total War from 2015 (which I guess is the time I and my friend installed Roma Surrectum 2, it was a long time ago so I don't remember the exact date) without the original icon. I attempt to uninstall it but I get the sign that says "The specified module could not be found". So what do you suggest I should do to be able to install Roma Surrectum 3?

[Jakoporeeno]

Okay, I merged Roma Surrectum 2.5 with RSIII and then put it in my Rome Total War Gold folder in common and it let me start the game but I've the got the "Please select an item from the list" sign whenever I try to start a campaign so I probably didn't install it correctly. And I still can't install a non-steam version because of the reasons I've already given so any help now would be appreciated.