I just started to play Morrowind a couple of days ago and I joined the Imperial Legion. Right now I'm doing a quest for Frald the White to find and kill an Imperial Legion deserter. I found the cave, but every time I go in there I get killed by the Daedra worshippers and I was wondering if anyone had any tips on defeating them. Also I'm a low level and I play on the Xbox 360. One more thing can anyone point in the direction to find an Imperial Skirt or an Imperial Templar Skirt.

This is old advice, but sound, you may need to build up your level and/or improve your armor.
Good "Shield" spells can also increase one's armor rating. These affect overall armor, rather than by location.

I remember some of the battles being overpowering too.

Thank you

Level-up.
Get better gear. Bring health potions.... standard RPG tactics.

The easiest way to get an Imperial Skirt is off of a dead guard. Not the best solution for a noble Legion officer, but it's true.
Templar skirts are even more rare. There's two in the entire game, both being worn by NPCs.

There are many other types of skirts for sale in clothing stores. Some of the common skirts look decent with armor.

One of the merchants in Caldera sells that purple skirt.