You're right, I didn't see many of the sights is correct and means I saw only a few or some of the number of interesting places.
But, I didn't see much of the sights is also correct. The idiom see much of means see frequently (especially in the recent past) or for long periods of time, and is typically used in the negated form. For example, I haven't seen much of my neighbors means I haven't seen my neighbors lately. This is valid even with a countable plural noun such as neighbors.
I didn't see much of the sights means that I spent very little time sightseeing. This means that I took in very little of what they had to offer, and likely (but not necessarily) saw numerically few of them if there were a large number.
Determiners are words like: a, the, this, that, my, your, no, one, two, many, much.
If a noun already has a determiner, we can't also use the determiners much or many with that noun:
- *much the work, *much our water, *much which water (ungrammatical)
- *many the people, *many my friends, *many these people (ungrammatical)
We also cannot use much or many with pronouns:
- *many them,*many us, *much it (ungrammatical)
When we want to use much or many with these phrases, we need to use a preposition phrase with the preposition of:
- much of the work, much of our water, much of that paper
- many of the people, many of my friends, many of these animals
- many of them, many of us, much of it
If the noun doesn't already have a determiner, we do not need to use the preposition of when we use the determiners much or many:
- much time, much water, much effort, much paper
- many people, many friends, many animals
The Original Poster's example
In the Original Poster's example they use the uncountable noun administration without another determiner apart from much. Because of this the OP doesn't need to use the preposition of:
There is so much administration to do.
*There is so much of administration to do. (ungrammatical)
However, if they wanted to use another determiner with the noun administration, then they would have to use much of. Here are some examples with the determiner this:
*There is so much this administration to do. (ungrammatical)
There is so much of this administration to do.
Hope this is helpful!
Best Answer
Underwear, like trousers or jeans, are referred to as a pair, because it's a throwback to when pants (pantaloons) originally came in two pieces - a matching pair. A person would put on one leg, tie it around their waist, then put on the other leg and do the same.
For more information, there is an excellent thread in EL&U, which references the following text:
Pants have obviously evolved, but the terminology still remains.
Therefore, "how many pairs of underwear" is correct usage. For example:
That being said however, in question form, we can use much, e.g.