@antmich, have a look at the install guide, this may help, https://documentation.meraki.com/MR/MR_Installation_Guides/MR46E_Installation_Guide.
There are six antenna connectors on the AP. One is the antenna for the scanning radio, one is the antenna for the IoT (BLE) radio, and the other four are the data serving radios. Those four are combined connectors connecting to both the 2.4GHz and 5 GHz radios, the antenna array being a 4x4 on both radios.
Since these access points have the scanning radio and IoT in them alongside the data serving radios there are only very specific antennas that can be used with them that are supported. These are on the datasheet that @Inderdeep referenced, under ordering information.