A Microsoft file hosting and synchronization service.
Standard DVDs only hold about 4GB of data. That probably will not work for you.
Microsoft 365 Basic cloud storage costs only $1.99 per month and gives you 100GB of storage. That is so much better in my opinion.
https://www.microsoft.com/en-us/microsoft-365/onedrive/onedrive-plans-and-pricing
If you don't want to use cloud storage, an external hard drive will work great as well.
To keep your files doubly safe, I suggest using both cloud storage and an external drive.