Someone please help me 😂😩😭.

My 2 year old girls are ready, I promise. They know when, and how, and why to use the potty. They love to sit on it, they know where it is, BUT THEY REFUSE TO USE IT! How do I get them out of diapers and on the potty? I’m currently 24 weeks with their new brother and the thought of continuing to buy them diapers and this new one diapers is overwhelming. I’ve tried all the tips and tricks family and friends have to offer. I’m at a loss here.