Need FM antenna for receiver setup

Hello All,

We are trying to setup streaming FM radio for our small office network. For that we bought 3 AM/FM digital receivers, each tuned to a different station, which are connected to a PC with 3 sound cards (see pictures attached).

I'd like to have your opinion about:
1. What kind of antenna should I use for this setup? Single ended? differential?
2. Is the ground terminal of the receiver is where the antenna should be connected?
3. How should I split the antenna to three receivers?

Looking forward to your replies,
Thanks,
P.