My Passport Ultra not working with iMac when first used with a PC

I used my WD Passport Ultra with a Windows PC. this was to recover some lost data (some of which I managed to recover) the PC went down and Now I’m using an iMac. Now, how do I partition this External hard drive (WD Passport Ultra) in order for me to use it on my iMac without losing the data that is on this drive already. Thanks!!
Much Help Needed!!!

Presumably you formatted it NTFS, or it came out of the box that way. On Macs, that format is supported but read only. If you expect to use it on both Mac and PC, you’ll need to use a file system supported by both, such as ExFAT.

Thanks Tony!

Of course, when you format it ExFAT you will lose all data on it, so save the data beforehand. ExFAT limits file size to 4GB, I believe.

This software called the ‘Stellar Partition Manager’ can work on NTFS hard drive and also on HFS, FAT and EXFAT. Overall its a perfect Disk Utility alternative but it isn’t free of cost. You may have a look at it and I suggest not to format your hard drive and better look for a Windows system nearby. Safeguard the data and format the NTFS hard drive to EXFAT so that you can use it for Mac and Windows file transfer. Thanks.