Step 2: Select Anonymize
After selecting the contacts > choose action > "Anonymize"
Step 3: Confirm
For single selection of specific contacts > Apply > Confirm
For filtering the list through search (e.g., target group) > Apply to all > Confirm
Open the contact database ("Contacts") of the account > Select "More Filters" in the search > Choose "show" or "only anonymized" for anonymized > Confirm the search by clicking the magnifying glass