Naturally, it was a Phishing email (your NFT has an offer!!!) that reminded me to check the wallet. Losing access to the wallet means the funds are lost.
Metamask uses a secret recovery phrase, with which you can import your wallet to a new machine. But I don't have the phrase...
So, Metamask provides a method to recover the phrase from a backup. They note that if the extension is uninstalled from your browser, the database may be wiped out.
The file location shown in MetaMask's support article is not exactly right:
If you have a backup, you can navigate to the Library file location in your user account. There you will find a low numbered database file, like 000005.ldb
You can load that file into the decryptor provided by Metamask, and recover the phrase.
Here's what I found that differs from the support article: The file location is in the user profile:
On a Mac, the location of the folder is: /Users/*username*/Library/Application Support/Google/Chrome/Default/Local Extension Settings/nkbihfbeogaeaoehlefnkodbefgpgknn
If the Library folder is hidden: Select your user account in the Finder window. Hold down Command-Shift-. (period) to show the hidden Library folder under your user account.
I copied the file to my desktop temporarily to make it easy to select from the Github tool.
This process took a long time because I had to find a TimeMachine backup from the old machine. I had to figure out how to open a backup from a different machine, [Hold down the option key and select Browse Other Backup Disks] but doing that was no help because I could not access the hidden files! So, I just navigated into the backup archive to find my files and used the CMD-Shift-. option to show the hidden folders.