If the Toshiba external drive was used for Windows PC, the file format could be NTFS, exFAT, or FAT32. And NTFS is a Windows-exclusive file system, therefore, you may need to format the Toshiba drive on Mac. In case the file system is exFAT or FAT32, you can directly use it on Mac without any limitations.
First of all, check the file system of the Toshiba external drive via the Mac's Disk Utility. Open Finder > Applications > Utilities, launch Disk Utility, click View > Show All Devices, and click the connected Toshiba drive on the left list, then check the drive info on the right pane, it shows the file format under the drive name.
In case the file format is NTFS, the Toshiba external drive is read-only on Mac because macOS doesn't support this file system by default. Given that there is nothing on the drive as you have deleted all, you can directly format NTFS on Mac. If you have kept important files on the NTFS drive, and want to use it for both macOS and Windows, you can try NTFS for Mac software such as iBoysoft NTFS for Mac.
For exFAT and FAT32 file systems, you can directly use the drive for Mac to read and write data. Or you want to completely erase the drive, or choose Mac OS Extended, the file system recommended for macOS Sierra and earlier, you also need to format an external hard drive on Mac.