macOS can read and write exFAT without limitations. To transfer files between two external hard drives, you should first connect both drives to your Mac USB ports, then open the exFAT Seagate drive in Finder or click the disk icon on Desktop, then select all the files you want to transfer, drag-drop or copy-paste them to the APFS Toshiba either from the Finder's sidebar or the desktop disk icon.
In case there are a lot of files you want to move, you can create a disk image on Mac for the Seagate drive or clone the drive on Mac via iBoysoft DiskGeerker, choosing the APFS Toshiba as the destination disk, the whole process is fast, you should know that this will erase the current contents on the Toshiba drive.
