So your DM was mostly in the wrong here. Sleet Storm makes a specific sized area heavily obscured. The DMG and PHB explain how to treat a heavily obscured area.

A heavily obscured area—such as Darkness, opaque fog, or dense foliage—blocks vision entirely. A creature effectively suffers from the Blinded condition when trying to see something in that area.

So if you and your party were in that area you would use the Blinded condition rules. Which are as follows.

A blinded creature can’t see and automatically fails any ability check that requires sight. Attack rolls against the creature have advantage, and the creature’s Attack Rolls have disadvantage

So, there are some caveats to what you're DM ruled. If your party was trying to find the enemy by making Perception checks or Investigation checks by using their eyes they would have automatically failed.

If they had other means of locating the enemy, such as blindsight or the locate creature spell, then they could have found the enemy.

If your party was already close enough to attack before the sleet storm spell went off, then you could have still made attacks, just with Disadvantage.

If you were able to locate the enemy or where close enough to attack, then the majority of your spells would have worked.

However if you were far away before the spell went off, and the enemy used the Hide action to hide, then any spell that specifies that a creature that you can see, would fail. But not every spell has that qualifier.

Some spells just have you target an area, or project outwards from yourself.