Yes, you will likely need a longer chain to accommodate the increased cassette size. The chain sizing and installation instructions for drivetrains that use a rear derailleur hanger are in the eTap AXS systems manual: Chain installation.
For full-mount derailleurs that don't use a derailleur hanger, the instructions are here: Full-mount chain length guide.
When changing cassette, an upgrade of the rear derailleur may also be necessary. For more info on compatibility, see our AXS Components Compatibility Map.