memory card

Can anybody help me please, im having trouble when i export a image from lightroom 5 to my memory card, when i took it to be printed the copy was under exposed when printed out, i dont no why.

Formatted on my D750, then shooting, my PC (Windows 7 premium) will not open the card. It gives a message saying the card must be formatted. I did format it in the PC, took photos, and it did then open. I would rather format it in the camera, for that probably has some benefits.I would think...