Free way to crosspost from eBay to Mercari/Poshmark?

I'm currently trying to clear out my closet, with about 250 ads on eBay. Is there a cheap way (or free) to crosspost from eBay to Mercari, Poshmark or other sites?

A trial version or cheap software would be nice. Hoping to spend not more than $50 a month or so.

Thanks!