Current best way to accomplish this. I use my favorite D-3 which has no WiFi options Thanks for your time.
The Nikon D3 uses Compact Flash for storage of image data, I believe. It MIGHT be possible to use an SD to CF card adapter which would them allow you to use an SD card with an integrated WiFi hardware to connect via WiFi with your mobile phone. It also MIGHT be rather slow to transfer image files, depending on their sizes. We talking large RAW files, or small or medium jpgs perhaps?
I have never done this, but I do know some folks have had pretty good luck with SD type cards with their built in WiFI networking hardware. It might be worth a try.
Perhaps there are readers here with actual experience with SD cards with WIFI adapters in the D3.
I don't think there are reliable CF cards with WiFi adapters, at least none that popped up in a google search for me.
An alternative that apparently works pretty well, is a CF card reader that plugs into an iPhone - check Amazon for CF card reader for iPhone ( also reads CF, SD or micro SD cards) and is cheap at 25 bucks. You have to take the card out of your camera to transfer, but it does seem to work pretty good according to reviewers on Amazon, especially to an iPad Pro or an iPhone.