Hey there, @CBM2. 

Thanks for reaching out to the Community for support. Along with what @BigRedConsulting said above, I'm happy to provide some guidance for updating from 2013 to 2021. 

Before you update your company file, it's always best to first create a back up in the 2013 version. I've included the steps below on how to create a backup. 

1. Open the File menu at the top.

2. Choose Back Up Company, then Create Local Backup. 

3. Click Next, then choose where you want to save your backup copy. 

Once you've saved your backup of the company file, you can now install QuickBooks 2021. You can use the link I've included below to download the installer. 

• https://downloads.quickbooks.com/app/qbdt/products

After you've downloaded the installer, it's time to run it. Let me show you how below. 

1. Open the file QuickBooks.exe you downloaded.
2. Follow the onscreen instructions. Accept the software license agreement and then hit Next.
3. Enter your Product and License numbers. Then click Next.
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Check out Install QuickBooks Desktop for further details about installing QuickBooks. 

For additional help, I'm adding this article that you may find helpful: Upgrade your company files after switching to a new version of QuickBooks Desktop.

Please keep me posted if you have any other concerns about this process. I want to make sure everything is taken care of for you. You can reach out to the Community at any time. Take care and have a great day!