If you still have songs uploaded to Google Play Music, you'll lose these permanently if you don't export them before February 24. Google has sent out its last email reminder to Play Music users. According to the email, "On February 24, 2021, we will delete all of your Google Play Music data. This includes your music library with any uploads, purchases and anything you've added from Google Play Music. After this date, there will be no way to recover it."
For those who already used the transfer tool, you still have the option to use it one last time. According to Google, "You've already transferred to YouTube Music. But, if you've made any changes, you still have the option to transfer again so your music library is up to date. If you would like to download your Google Play Music library and data, you can do so with Google Takeout before February 24, 2021." You can also check out this link to find out your export options.
Source: 9to5Google