This is literally impossible to tell without more information. According to Wikipedia Mercury weighs about 3.285 × 10^23 kg, about 10^20 times more than most s

This is literally impossible to tell without more information. According to Wikipedia Mercury weighs about 3.285 × 10^23 kg, about 10^20 times more than most satellites. You'd need much more than 1000 satellites (or have much heavier satellites) to significantly impact the orbit. OTOH, if you'd have sensitive enough instruments you could measure the effect of even a single gravity assist.