EEG ADC for pi 4b

Hi i was hoping you could help me. I want to write an brain eeg program and want a system to test it on. I saw your mikroe eeg circuit and ive got two on back order. i was hoping to run it on my raspberry pi 4b and saw your dual adapter thing for the click but i curious as to how it would work as the pi doesnt have any adc’s and there isnt a chip on the adapter. do i need to buy an adc and if so which one. the sample rate has to be high 2000-3000sps. i can see a few that are reasonable or even over the top, mikroe 15,6,10,13,18 clicks. which one is good for this application?

My expertise on those are limited, maybe post in the Mikroe forum