I filed an extension for 2021, but I can't find the form anywhere on the website. Does anyone know where it's located?

See this TurboTax support FAQ for printing the extension request - https://ttlc.intuit.com/turbotax-support/en-us/help-article/printers-printing/print-4868-extension-form-e-filing-turbotax-easy/L6MJM5wAT_US_en_US?uid=l4vm01ul

if you are going to e-file it does not need to be submitted. but like your entire return, you should save a PDF of all documents