Sure you can. The meals at Hogwarts are conjured - Dumbledore just waves his hands and kaboom, a huge feast appears on the table.
I’m sure at some point Rowling wrote you can’t conjure food, but in fact it’s done many times (mostly by Dumbledore) but then on innumerable other occasions wizards act as if they’ve forgotten you can conjure food. The HP universe is wildly illogical and inconsistent, so there’s not a lot of point in trying to fanwank this stuff.
I’d agree that the most obvious solution to the Death Eater problem is the British Army. Unless a wizard has specifically raised a spell that will shield them from powerful projectiles, a 5.56 bullet will kill them just as well as it’ll kill anyone, and they don’t seem to have any conception of fighting someone further away than a hundred yards, or concealmet, or anything like that. Indeed, there seems to be no soldiering in the wizard world; the Ministry of Magic has a law enforcement organization, but not a military, and Voldemort’s people are just thugs. Their methods of defense and fighting are specifically tailored to fight other wizards, not soldiers. Against a Muggle army (which would presumably have to be allowed access into the magic world with a little help from friendly wizards) they’d be preposterously unprepared for professional killers shooting at them from beyond visual range, and would collapse in terror and panic in about two days.