First you need to know the email address associated with their Google Drive / Docs account. Then go to your google drive and use the advanced search (click the search options icon) and find the "shared to" field and put in their google drive email address. Then select the files from which you want to remove their access (to select all, CTRL-A on Windows, CMD-A on Mac) and then click the Share icon, and change them from Editor/Commenter/Viewer to "Remove".
Watch video Google Drive files -- Remove someone's access / prevent ex-assistant from accessing docs/sheets online without registration, duration hours minute second in high quality. This video was added by user George Kao Business 24 November 2021, don't forget to share it with your friends and acquaintances, it has been viewed on our site 42,902 once and liked it 217 people.