No devices show up under my apple business account.

There is so much to your question.

1. If the devices are not showing up in the Devices section, you will need to add them manually. You will need a macOS device running Apple Configurator 2 for this. Note that devices can be removed by wiping for the first 30 days after being added manually.
2. You can use Apple Configurator 2 for setup and deployment, but it is highly recommended to look into a Mobile Device Management (MDM) platform for this. Some options are Jamf Now (free for the first 3 devices, $2/device/month for devices 4+), Jamf Pro ($3.33/device/month, minimum 50 devices), Mosyle ($1/device/month), Fleetsmith (free for the first 10 devices, $8.25/device/month for devices 11+), Kandji ($400/month for up to 100 devices), and Apple Business Essentials ($2.99/device/month for single device)

Get started using Apple Business Manager or Apple School Manager with Mobile Device Management - Apple Support

We added our first MAC to the account. Was purchased then taken to the store with the receipt and added to our Business account. They told us it would take 2-48 hours to show up. Today is day 3 and I need to deploy this device.

If the device is new, you can use Configurator for iPhone to enroll a macOS device.

Apple Configurator User Guide - Apple Support