If your Macbook Pro have DVD drive, then you can replace that DVD drive with additional hard drive/SSD. So you will have two hard drives working with your Mac.
Or you can replace the old hard drive with a higher capacity one.
Your Mac has SSD (not hard drive). The maximum size of SSD I can see is 1TB (1024 GB) but I'm not sure Apple stores have them in stock. It costs up to $1000 to the SSD itself excluding labour.
You're most welcome !