Hi I just bought iPhone 12 Pro Max from apple store but I need new one 13 so how I can take that one

Normally you have 14 days to return it for any reason. But there is no harm in trying.

Returns & Refunds - Shopping Help - Apple

One month ago is not "just bought", you only have 14 days to return it for a refund. You can trade it in towards a new one and pay the difference in the cost. Check with your cell service provider first, many of them have better deals going for trade-ins.

Return the 12 Pro Max to wherever you purchased it for a refund and then order the 13 Pro Max.