how do I transfer files off NTSF external hard drive on to mac

I have had an external hard drive for a long time now. I bought it after I bought the iMac in 2010. it is a Toshiba 1TB. I have used it to store photos on. It has worked for me for many years on my iMac. It was formatted for NTSF, I guess I had a reason at the time. However, I updated it High Sierra and the external hard drive will no longer works in that I can see the files, but I can not copy, or edit. It says in the little box with all the users I have read and write permission but above that, it says I only have read permission. I can't copy and paste the files on to my internal hard drive, it allows me to copy, but not paste. Does anyone know of a way I can save a life time of photos?

thanks,

Beth