It depends on how you restore it. No data is erased unless you follow the last method (restoring everything).
To restore individual files:
Manually copy the desired files over from the Time Machine drive, or associate the TM drive with your new MacBook Pro:
- Connect the TM drive, and enter the encryption password if applicable.
- Select Time Machine in the menu bar. Hold down the Option key and click on Browse Other Backup Disks.
- Select the TM drive, then click Use Selected Disk.
- Open the Time Machine app on your Mac, or click on Time Machine in the menu bar and select Enter Time Machine.
To selectively migrate types of data:
- On your new Mac, open Migration Assistant. It's located in the Utilities folder inside the Applications folder.
- When prompted, choose to restore "From another Mac, Time Machine backup or startup disk".
- Connect the TM drive and follow the onscreen instructions.
To Restore EVERYTHING
WARNING: These steps will erase your new Mac and replace it with the contents of the selected backup.
- Boot into macOS Recovery: Hold down Command-R as you turn on or restart your Mac.
- When the macOS Utilities window appears, select Restore from Time Machine.
- Follow the onscreen prompts to erase your Mac and replace it with the contents of a backup of your choice.