How to reformat to mac without losing files

I purchased my passport 1 tb to store my photos on as  I replaced my PC with a MAC. I was able to pull photos from the pc and can access them from my passport on my mac. I cannot add more photos off my mac to my passport. I was initially told to format it to the mac before i used it on the pc. Now it is formatted to windows. any suggestions  without lossing my photos?

You would have to copy the data on your hard drive to your mac, then reformat it with the Disk Utility application.  Click on the Erase tab, choose your external hard drive and select Mac OS Extended (Journaled) and then click Erase…

Then simply drag and drop your data onto your newly formatted disk.

Or if you wish to be able to transfer back and forth (PC to Mac or Mac to PC), select the FAT32 format.

you don’t have to reformat if you don’t want…

You can user NTFS-3Gand read and write with the drive as is