https://wccftech.com/m1-ipad-pro-thunderbolt-3-data-transfer-speeds/

For the first time, Apple has added Thunderbolt 3 support to its M1 iPad Pro, meaning that in addition to hooking it up to an external monitor for increasing your workspace, users can experience faster data transfers, but by how much exactly? This little test shows the results that you are looking for, and while they are satisfactory, the M1 iPad Pro is still slower than a MacBook Pro.

Created Tech made a video on YouTube showing the M1 iPad Pro file transfer speeds using the Sabrent XTRM-Q Thunderbolt 3 external drive. He states that after testing the MacBook Pro earlier, the write speeds recorded were 2401MB/s, which is incredible but given that both the port and the drive support the Thunderbolt 3 protocol, looking at the results is not surprising.