I have a Mac snowleopard from 2010. I am buying a new Mac soon how can I transfer data

You can use Migration Assistant, a program provided by Apple for transferring your files from your old computer to your new computer. It is very easy to use. Be sure to read and follow its instructions. Basically, the process is as follows.

You first begin by starting the process of setting up your new computer. You will be asked if you wish to transfer files. Respond YES and follow the instructions you will be given.

·      You will be told to turn both computers on and activate Migration Assistant in the old computer.

·      The computers should be connected with a cable to facilitate the transfer. Wi-Fi is not suited for a transfer of so much data and corruption often results. If you must use it, make sure the two computers are located close together.

·      You will be given several options of what to transfer. You will likely want to transfer your settings and preferences.

·      You can transfer all or none of your files. You do not have an option to select certain files to transfer. If you wish to do that, then do so manually.

·      You can transfer all or none of your installed apps. I think you will be better served to download and reinstall clean versions.

·      The old computer's operating system will not be transferred. No data from the old computer is erased.

·      Allow for up to an hour for the transfer process to complete once you start it.

·      When that is successful, you can log into the new Mac with the old User Account name and password and delete the brand-new user or leave it in place as a second admin account.

Enjoy your new Mac.

I hope this is helpful. Good luck.

One Size does Not fit All 

If the new computer is going to be the Apple Silicon M1 / M2 Equipped Computer - would suggest Only Migrating the User Account and nothing more.

Some have had success and others have been left with a mess when Migrating everything.

1 - Apple Silicon with Ventura macOS 13 Only Support everything 64 bit and there is no workaround.

2 - Issues that may exist on the older computer will be migrated to the New Computer. This would badly pollute the new Original and Pristine installation of the new OS.

3 -  Applications, extensions and Software Drivers may or may not even work on the new computer.

4 - IMHO - it would be best to only install new application etc Directly from the Developer or the Apple Apps Store.

5 - Due Diligence on New Applications and make sure they are Ventura / Monterey / Big Sur compatible and factor in the ARMs CPU of the Apple Silicon Computer  

6 - The User can always use Time Machine Backup at a later time to restore individual files.

Transfer to a new Mac with Migration Assistant - Apple Support