back up to time machine, then to portable drive ssd T7 Shield

In Theory - Time Machine Backup should or may Convert the Drive to the required APFS drive format.

Personally, I would be more inclined to use the below Apple Support Method to insure it is done right.

Erase and reformat a storage device in Disk Utility on Mac

Excerpt from above link

In Ventura Settings:

General > Time Machine and click [+] to add your mounted APFS Time Machine drive. Select options and choose Back up frequency to Automatically Every Hour, and do not change anything placed in Exclude from Backups by default. Add anything else that you don't want backed up here. Click Done.

Control Center > Time Machine > Show in Menu Bar.

Since I am using the Dark appearance mode, here is that Menu Bar Time Machine panel showing the last backup was successful:

During a backup you will see x% of y progress shown in that menu.

Never unplug your Time Machine drive without first looking to see how close you are to the next backup, and then if time, right-click on that drive and select Eject "Drive Name". A corrupted Time Machine drive will need to be mounted in Disk Utility where you run First Aid on it.

I use 2TB Crucial X8 (1050MB/s) drives for Time Machine backups. Too many years of people reporting interoperability issues with Samsung T5/T7 drives for me to go that route. The Crucial drives are rock solid on several Intel/M1 Macs.