So you have a database that is 1750 GB full of which 700 MB is not allocated if I understand correctly. Then you can shrink the database at maximum 700 MB to 1749 GB (rounded). That is not particular meaningful.

You will have to add more disk. And if that is not an option, you will need to create some free space in the database. Here are a couple of options do this:

Although, with only 700 MB free, the latter two options may not really be available to you. If you have a 200 GB table you want to compress down to 150 GB, you will need 150 GB of disk space available, since SQL Server builds a new index structure. It does not compress in place.

Once you have freed up space inside the database, you could start shrinking. Although the only reason you would do that is that you desperately need the disk space for something else. Because I suspect that you will continue to pour data into that database.