How do I back up on to a separate disc as I have 23K photos taking up to much space?

[iMore Question]

How do i back up on to a separate disc as I have 23K photos taking up to much space

I tried to back up onto a seagate 4tb drive i purchased now i find that no back up was made and i am unable to access the seagate to do 1st aid or reformat it. I need to move my pictures as my iMac keeps telling me i have low space on the start up disc. Pleas help.
PS: the seagate is being sent back to supplier as non functioning.

 

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Re: How do i back up on to a separate disc as I have 23K photos taking up to much space

Perhaps cloud storage would be of help to you. There are plenty of options to choose from