If you have received payment in DJED or IUSD, then you will first need to convert this to ADA. You can do so at the best price by using https://www.dexhunter.io/. It is also possible to do swaps inside some of the wallet apps (might give you slightly worse price).
Please follow the link to the guide containing the step-by-step guidance on converting your ADA to Kenyan shilling.
https://www.lidonation.com/en/posts/ada-conversion-to-kenyan-shillings-using-yellow-card
You can use Kotani pay to convert USDC to MPesa. Please contact Simon for guidance on how this can be done.