Cannot connect my Raspberry Pi 4+ to Arduino Pico

The serial port does not appear. '/dev/ttyACM0' when board is plugged in.

 Version 21.10

mark@mark-pi:~$ uname -a
Linux mark-pi 5.13.0-1010-raspi #12-Ubuntu SMP PREEMPT Tue Nov 9 15:30:22 UTC 2021 aarch64 aarch64 aarch64 GNU/Linux
mark@mark-pi:~$ lsb_release -crid
Distributor ID: Ubuntu
Description: Ubuntu 21.10
Release: 21.10
Codename: impish
mark@mark-pi:~$ apt-cache policy thunderbird
thunderbird:
  Installed: 1:91.3.1+build1-0ubuntu0.21.10.1
  Candidate: 1:91.3.1+build1-0ubuntu0.21.10.1
  Version table:
 *** 1:91.3.1+build1-0ubuntu0.21.10.1 500
        500 http://ports.ubuntu.com/ubuntu-ports impish-updates/main arm64 Packages
        500 http://ports.ubuntu.com/ubuntu-ports impish-security/main arm64 Packages
        100 /var/lib/dpkg/status
     1:91.1.2+build1-0ubuntu1 500
        500 http://ports.ubuntu.com/ubuntu-ports impish/main arm64 Packages