Merging 2 Shopify stores for US and CA into 1 Shopify store with 2 markets

[SolutionG]

I'm helping a client with 2 Shopify stores setup with 1 for CA and 1 for USA, currently paying for 2 plans

They are building a new store with 2 markets instead within the CA store, so they only need to pay for 1 plan.

The domain for CA is set to the main domain name, while the USA store has a us. subdomain.

Their Klaviyo is only connected to their CA store only because they did not know how to connect 2 stores in 1 integration (you can't, you need 2 paid acounts).

They want to move all the customer profiles from the USA store plan to the CA store plan, then sync all customers back to Klaviyo to make sure nothing is missing once they launch the new site on the CA store.

Is it possible? How does that work?