How do i ask her out and is this a good plan for a date?

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 gas 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 just call her i dont wanna text?