How to ask out my ex girlfriend?

was thinking of taking her to a concert the catch is this girl is my ex girlfriend of 10 months. she broke up with me about 3 months ago. she hasnt been the nicest through the breakup and has been partying and has changed alot but i have gave her space of no contact this last month except for 1 day i talked to her. i still love her so im trying to get back together, as far as i know she hasnt dated anyone else but she might have been intimate with another guy. Also how can i ask her out ? ill be seeing her this week cause i have to pick something up from her so what should i say when i see her. do i just get the thing and then ask about going out or should i do small talk then ask