my 2003 nissan sentra se-r have a misfire on cylinder one how do i know which is cylinder one

what size engine does it have?

2.5

Cylinder #1 is the one on the passenger side.

If i change the coil can that fix my misfire

If the coil is the problem. It won't do anything for the problem if the plug is defective, or the wiring, or if there is low compression. Swap it with another one and see if the problem goes away or follows the coil cap. Check compression.

how do i check the compression and when u said swap with another one what dou mean

Move the coil cap from cylinder #1 to another one, like #4 and see what happens.

You need a compression tester. These can be borrowed from stores like O'Reilly's, Advanced, Autozone, etc. Remove the spark plug and insert the compression tester into the cylinder opening and crank the engine for about 5 seconds. Note reading, release pressure, and repeat on the other cylinders. You want compression to not vary by more than 15 PSI from highest to lowest.

ok if the compression is wrong what are my options. But if is ok what else can i do. my car have done the misfire 3 times in the last past 6 month only happens when i start the car thanks for ur help

If the compression is bad, 3 options, replace the engine, fix the rings or valves, or live with it. If the compression is low, squirt a little sewing machine oil (LESS than a teaspoon) into the cylinder and check the compression again. If the compression goes up, bad rings, if it stays the same, bad valves.

If it's only shown the misfire code 3 times in the last 6 months, I would suspect a coil cap or wiring problems.

If the compression is fine, then it's going to be either an injector problem(I forgot this one earlier), coil cap wiring issue, or a bad coil cap/spark plug.