Can I use my Ipad 2 Adapter and a USB cable for Airpods to charge my Iphone 13 Pro Max?

sure, could also use the ac charger from any other apple device which have a connector that fit your charging cable

Recently got 13 Pro Max also & used my other chargers for about 2 wks. Broke down & bought the USB-C charging block so I could use the cable the phone came with. WOW...it charges way faster!