My Ex Is Withholding My Belongings Until I 'apologize For Everything.' We Broke Up Months Ago And She Won't Let Me Get My Stuff. Can I Call The Police For This?

Location: California

My ex girlfriend and I broke up about 4 months ago. It wasn't a great breakup but it wasn't violent or anything, we just weren't working out. When I moved out I left some stuff at her place because I was moving into a temporary situation and didn't have room for everything. We agreed I'd come get it once I got settled.

Well now I have my own place and I've been asking for my stuff back for the past 6 weeks. Every time Im doing something random on my phone like playing on rolling riches i get the urge to text her she either ignores me or says I can have it back once I "apologize for everything I put her through" and "admit what I did wrong." I've tried to be reasonable and ask what specifically she wants me to apologize for but she just says "you know what you did." The problem is there's some expensive stuff in there. My laptop, some tools that belonged to my grandfather, clothes, important documents like my birth certificate and social security card. I need this stuff back.
I asked if I could just come by with a friend to grab it and she said if I show up she'll call the cops on me for trespassing and harassment. But like... it's MY stuff?

Can I actually call the police for this? Would they help me get my belongings or would they say it's a civil matter? I don't want to waste their time but I also don't know what else to do. I'm not apologizing for shit I didn't do just to get my own property back.

Any advice appreciated.