Erasing data on an old MacBook pro

What to do before you sell, give away or trade in your Mac – Apple Support (UK)

Of course you could remove the hard drive, but it would make the computer useless to whoever you give it too. Mind you, they may want to put an SSD in the computer instead.

If it uses a hard drive, then I highly recommend to first enable Filevault and let the encryption process finish, otherwise you need to write zeroes to the whole hard drive to destroy your personal data, but this is difficult to do since Apple has removed the secure erase feature of writing zeroes to a drive from recent versions of Disk Utility. Without overwriting the hard drive with zeroes or first encrypting the drive anyone with access to the drive can use a data recovery app to recover your personal data. Unfortunately the instructions in Apple's current articles assume the computer is either using an SSD or that the hard drive has Filevault enabled.

If the laptop uses an SSD, then following Apple's instructions should be sufficient to destroy the data on the SSD due to how SSDs work.