how we can replace the T8 lamps with T8 LED tube??

 

For existing fixtures:
http://www.homedepot.com/p/Philips-4-ft-T8-17-Watt-Daylight-Linear-LED-Light-Bulb-456608/206278132

Or just swap out the entire fixture - they are getting cheaper all the time.

 

how we can replace the T8 lamps with T8 LED tube??

Buy ones that are compatible with your existing ballast or swap out the ballast with one that works with the LED tubes.

I bought LED tubes and had to change the ballast to instant start.

 

how we can replace the T8 lamps with T8 LED tube??

Replace the whole fixture for $19.95.

Or you select a pair of these (Link below) and pull the balast off of the fixture and (dare aI say on this website) directly wire these LED T8 LED bulbs to Mains- not likely a controversial recommendation since that is the manufacturers recommendation.

https://www.1000bulbs.com/category/double-ended-direct-wire-t8-tubes-4ft-3500k/