Extremely slow load times - what am I doing wrong?

I love the idea of the WD My Cloud (4TB), but when I transfer data from my external hard drives the unit the load times are extremely slow. I uploaded a 250GB external hard drive over my home network (ATT Uverse) and it took from Friday about noon until Sunday 5pm. I just finished loading a second external drive with about 400GB on it and it took from Thursday night through Monday morning. I am wondering what I may be doing wrong. Is this normal?

If I have to do this all once to get the data on there, fine, but I can’t shake the nagging feeling that something is wrong. Thank you very much for your help.

what are you using to copy the data? File explorer / Finder are much better for local use then the WD apps.

you mention Uvers. Are you doing this locally? or over the Internet?