How to best track lead conversions?

Hi, I hope someone can help. Currently, all potential leads (cold & warm) remain leads until they actually purchase something from us. Then when they've purchased, they are converted from Lead to Account and a Sales Order is created. We do not use Potentials...I don't understand how they work.

I would like to be able to track how many leads we have and how many are converted to accounts in a period.

Is my best bet to use Potentials and Campaigns, or use Status, and then use Pulse to track the Status changes?

We are currently unable to pull any reports that displays this type of data.

Thank you for reading.