Can we integrate shopify site with square reader

Hello All, I need help with my store. Before I used to sell via square online and in person via square pos app. I have recently migrated to Shopify and want to sell in person in markets.

Is there a way to keep using the old square reader and accept payments through it for my shopify store.

Also is there any Shopify support email for plus members? Or a call back feature I can use. The chat assistant is not working.

Please help!