As eluded to previously depends on where there at but also if they do know we exist as an intelligent civilisation likely it would be through leakage of our technology i.e. radio signals in to space. That limits them to being within 100 light years (close by) as radio broadcasts I think were first introduced in the early 20th century, for them to answer back then they would have to be within 50 light years (50 for it to get there, 50 to direct a message at us). What all of this does assume is that they have a huge sensitive receiver that would pick up barely noticeable radio signals which leaked out. If I were to hazard a guess I doubt any intelligent civilisation out there knows we exist at the moment, they may well know there is life of earth but not technologically advanced life, I am kind of leaning toward we would pick something up from them due to the likelihood that their advanced technologies would 'stick out' more maybe like FRBs we are seeing. Very interesting subject regardless, with many hypothesis' worth looking into.