Sophia here from Shopify. Welcome to the Shopify Community!
You're correct that the 1099-K form for Shopify Payments will be under Payouts > Documents. Are you using Shopify Payments exclusively, or are there other payment gateways like PayPal or manual payment methods enabled on your store? The 1099-K form is available when the total processed through Shopify Payments is $20,000 or higher and there are 200 or more transactions, so if orders came through outside of Shopify Payments, they wouldn't be included in these totals.
The 1099-K form issued in the Shopify admin is only for Shopify Payments, so it doesn't factor in transactions processed through other payment providers. As PayPal and Amazon Pay are a third-party payment providers, I recommend reviewing your accounts with them and contacting their support teams if necessary to find out whether they provide tax documents.
As I am unable to provide tax advice, please be sure to check with a local tax authority or accountant to make sure that your business files and remits taxes correctly. They will be able to provide accurate information and help you determine which documents you need for your tax reports.