I cannot do bootcamp but my hard disk only have machintos HD and Data
The simplest thing is to delete the "Data" partition and resize the Mac partition to take the whole area.

At that point, you are one click away from running BootCamp Assistant.

Options are to use Disk Utility to make an image of Data to an external drive (or perhaps to Macintosh HD if there is space). Another option is to clean as much files off Data or back it up to an external device.

It's really a balance between how valuable the files on "Data" are to you what step to take next.