Hello Felipe,
So you'll need to have a For Each cycle iterating over your string list, and you may have an Assign with other Text variable where you concatenate your values:

This means that, for each string value, you will concatenate it in your TotalText variable. However, using this approach, you'll have an extra ", " in the end of your string from the cycle, so you will need to remove it (after the cycle):

Do you want to show this value to the user as an input? Or is it a label? Sorry, I didn't understand that part properly. Can you please explain it a bit further? :)
Kind regards,
Rui Barradas