How do I export all of my forms

How do I export all of my forms into a single excel sheet?

Are you referring to the form submissions or the actual forms?

You can export all of your data by following this guide: https://www.jotform.com/help/374-How-to-export-all-of-your-data-at-once 

You cannot download ALL the submissions of ALL forms in one excel file. You can download the submissions for each forms as an individual excel file. Here's a guide that you can refer to: https://www.jotform.com/help/269-How-to-View-and-Export-Form-Submissions. But it is possible to combine your submissions from multiple forms and download them as a data file, you can use this app for that: https://apps.jotform.com/app/combine_submissions 

If I may also suggest, if you want the submissions on your forms to be on a Google spreadsheet, then you can simply integrate your forms there, here's a guide you can check: https://www.jotform.com/help/228-How-to-Integrate-Form-with-Google-Spreadsheet 

I hope that helps.