Can I use my current re-changer that I use for my IPhone 6 to use to charge my new iPhone 12 pro max

If you mean the charging brick and lightning cable which came with your iPhone 6, yes you can. At only 5W, it will charge you phone slowly, but it will charge your phone just fine.

Your new iPhone is coming with a USB C to Lightning cable. If you want to use the charging brick which came with your iPhone 6, you won't be able to use the new cable coming with your Phone.

Apple sells a 20W charging brick and there are loads of options on Amazon you can buy, which will charge you phone faster.

Here's a good one on Amazon that is very reasonably priced. --> https://www.amazon.com/Charger-Anker-Adapter-PowerPort-iPhone/dp/B07WRKXQ8W/ref=sr_1_1_sspa?crid=3MA5PZP3VSF4I&dchild=1&keywords=usb+c+20+watt+charger&qid=1605123118&sprefix=usb+c+20+w%2Caps%2C186&sr=8-1-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEyU1QxQ1IxNkcyMTdaJmVuY3J5cHRlZElkPUEwODY4NjUzVVMxSEJYV1RCRUxGJmVuY3J5cHRlZEFkSWQ9QTA1MTM5MTdJV1VLV0xDVkxDRDImd2lkZ2V0TmFtZT1zcF9hdGYmYWN0aW9uPWNsaWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVl

If you'd rather have the Apple Brick, buy this --> https://www.apple.com/shop/product/MHJA3AM/A/20w-usb-c-power-adapter?fnode=d884218142d1073aca7b78833bcc9ef67b9fae74bf72b9ae0fad18afb8ab26cc85a2269afac9c388395b1635d7a04ba08e62050c858f54b78a309f58c0206a1fde0f663ff25086322b6065182bb08ad6ec75761a8ae332880bf8306f8bc6ed79755ed70bceddad4824ce5630bbe144df