Replying to Crazy ex girlfriend lolol

Okay so I have this batshit crazy ex girlfriend who has equally crazy friends. I broke up with her about a month ago, and never got my shit back from her. Most of it wasn't important, just t shirts and whatnot. But there were a couple of things that i accidentally left at her house that had serious sentimental value to me, and I really want back. So I text her today saying "Hey, I'd really like it if i could come get my stuff. Can that happen?". So naturally, she starts shit immediately. She brings up old shit, and eventually gets her friends involved. This one kid, her "big brother" she calls him, is like twenty or twenty one, and for some reason is cool enough that he picks on kids who are 3+ years younger than him (I'm seventeen). This is the kid mind you, whose girlfriend fucked one of my friends while they were broken up and had been for months, and he slashed the kid's tires. So anyway, her friends have been blowing up my phone all night threatening all kinds of shit. I'm in no way afraid of them, I'm just wondering what the hell I'm supposed to do.