What is designated wiring of device . the wire attached to unit has 3 wire coming from it . which is which ? power , ground,etc.....

It's a pain to re-engineer this fixture for direct wiring just to save $8 over the correct fixture for the job (which would be what Lowes calls a *strip* rather than *linear* shoplight). The Greenlee step drill to properly put a 1/2" KO hole for a wire-entry connector in the too-thin sheetmetal will run you between $35 and $60. That said, if you make the decision to buy the correct tools and do surgery on the fixture, once you get inside you'll find US color-coded wiring. If you don't know what that color code is, my advice is to just use the plug to connect to a professionally wired outlet. :-)

The center lead is the ground lead. The two outer leads are power leads, "non-polarized" meaning you can wire hot and neutral to either.

Black is hot, white is neutral, and green is ground. There is only 2 wires coming from the new light. Black and white. Attach black to black and white to white from the ceiling. Attach the green wire or bare copper wire coming from the ceiling to the green ground screw you will find in a plastic bag with the light. There is a place on the light to put this screw.

I installed a new outlet in the box that used to house the old fixture connections. Install a new metal cover plate (to hold the outlet) after that, simply plug it in. If you don't know how to install an outlet, maybe you shouldn't. Check YouTube. Search "install electrical outlet".