Many of the users of the previous version of Solflare used a Keystore File to access their wallet. We have since transferred over to a Mnemonic phrase for technical reasons but you can still access your assets by uploading your Keystore File into a new Solflare Wallet.
This guide assumes you have made a new Solflare wallet with either a recovery phrase or a Ledger hardware device.
If you didn't you could follow these guides:
Access a Solflare wallet of yours via Solflare.com or Solflare Extension for Chrome/Firefox/etc (Extension download links available here: https://solflare.com/download)
Click the Profile Picture (at the top right)
Step 2 (three parts)
Click Import A New Wallet.
Click More Options.
Click Import Keystore File.
Step 3 (three parts)
Type in what name you want the account to be called.
Click Select Keystore File and upload the file from your files folder.
Type in your Keystore File password and click Add.
You're all Set
You'll be taken to the dashboard of the wallet associated with your Keystore file.
When you click on your account icon again in the top right corner, you'll see that you can easily navigate between your new Solflare wallet and the one you just imported with the Keystore File.
Please be aware: If you lost either your Keystore File or your Keystore File password, there is, unfortunately, no way to access the associated wallet.
Note: You'll need to repeat this process if you are ever logged out or are logging in on a new computer.