From Workshop Link
In order to get the id of a workshop mod, go to its workshop site, and look at the last number of its URL. That's your mod's id.
So for https://steamcommunity.com/sharedfiles/filedetails/?id=1682700568, the ID would be 1682700568.
In case of a subscribed workshop mod, you can look into the
modinfo.lua file that will be in that mod's directory. Open the file with a text editor, and look for a line like
id = "1682700568",. That number is your ID (without the quotation marks).