much clothes or many clothes

Solution 1:

Clothes, like oats, is both plural and uncountable.

• a bowl of *bean/beans, a bowl of *oat/oats, a bowl of rice/*rices

Since they're plural, clothes and oats take plural verbs, even if they are uncountable.

• The oats/beans were delicious.
• The rice/milk was delicious.
• The clothes are on the floor.
• The hat is on the floor.

As for much/many, it's more complex. Many of the clothes means considering each piece separately, and it's plural and essentially countable.

• Many of their clothes need repair.

If you want to use much, don't use clothes -- use clothing instead, because that's definitely mass and singular and works where clothes wouldn't:

• Much of their clothing was swept away by the storm.
• ?*Much of their clothes was swept away by the storm.