The deadline to apply for vote by mail is Oct 26th. You can apply here. From the NJ Voter Information portal:
“Please contact your county clerk to submit a request. If you would like to receive your ballot by mail you must request your ballot by Tuesday, October 26, 2021. Otherwise, you must get your vote-by-mail ballot in-person from your county clerk, by November 1st at 3 p.m. You have until 8 p.m. on Election Day to return your ballot to the Board of Elections in person or deposit it in one of your county’s secure authorized ballot drop boxes. You can also mail your ballot, it must be postmarked on or before 8:00 p.m. November 2 and be received by your county’s Board of Elections on or before November 8.
You can find your County Clerk contact information here.”