ok so with a quick search since mars gets 44% of the light on earth. so with some math we get about 1.5 lx but wait, mars's atmosphere is different than earth's we can assume mars's twilight is around 1 lx or at least less than 1.5 lx. Now keep in mind this is using civil twilight measurements. This is as far as I can go to answering but I think it's safe to assume its <1 lx. math:
3.4 lx*44%=1.54 lx
But wait there's more. Here I'm including some more math that might not make sense. so because 0.00001 of light is scattered per meter at atmospheric pressure. blah blah blah, there is only 0.00108 of the light that gets scattered... safe to assume twilight is very dark after all. and that's a generous number, very generous.
in conclusion mars twilight is very dark. the first answer has math that definitely works but doesn't take into account the atmosphere, the second takes care of the atmosphere but the answer I get seems off. the answer when combined is 0.003 lx + moonlight so I'll say an even (maybe a bit more) 0.01 lx to 0.02 lx, still very dim. (take into account that this is an approximation) but the image here shows it is similar to night time which makes sense. source
edit: taking into account dust we can assume this number is higher, but not by much because i cant calculate how exactly it would be, i can give a educated guess of <0.5 lx but >0.1 lx but i assume this number would change over time with weather.