Not sure what version of the question you had (audio vs. translation) but we know it has more than one pocket because it's using the plural "des poches". As far as singular, "Du" is masculine (de le) and since "poche" is feminine, one would use "de la". Not sure if this is right but I imagine for one pocket it may be "un pantalon avec de la poche" or even "Le pantalon a une poche" (the pants has one(a) pocket).
I don't think "de la poche" works since, I can't really see "poche" or "pocket" as being used as a non-count noun, as you might use "fromage", "lait" etc (eg "Il mange du pain"). Not in this context, at least.
It may be possible to think up some (unusual) sentence eg, in English
There's still some pocket left but most of it has worn away
but I would suggest that even then, we'd be more likely to say something like "some of
thepocket" or "part of
a/the pocket". See, for example, this :
car s'il reste une partie de la poche ...
in an 18th century medical work.
That's not what you would say in English. You'd say "I am wearing pants/a pair of pants with pockets." "Some pockets" is redundant to say in English, and simply isn't said by anyone when referring to the clothes they're wearing. By all means, report it if you think it should be accepted though. It technically means the same thing.
The first time I received this sentence, I wrote "I wear a trouser with pockets" and it said it should be trousers. This time I wrote "I am wearing a trousers with pockets" and it said it should be "I wear pants with pockets". What's right and I'm not going to translating french to English, I just want to understand it.
If it is theoretically correct in English and is understood as such by its native tongue it should be accepted. I am wearing pants with some pockets. Some pockets is not incorrect as it is some pockets. And is understood as such when you are forced to translate it directly. I would be more lenient towards this rule... for the soul reason that we are already confused enough as it is. My goal is to learn french and not on how to translate it with utter perfection from french to English.