Do you sell the iMac with 1 or 2 TB

1 or 2 Tb of what? Memory? Storage?

Buy iMac from $1299 - Apple

Select and read the the purchase options.

No one here is an Apple employee, just users like yourself. You are not speaking to Apple here.

Looking at the Apple Store page for the 24" M1 iMac, it appears that the custom-order storage options are

• 256 GB / 512 GB / 1 TB on models without USB3 and Ethernet ports
• 256 GB / 512 GB / 1 TB / 2 TB on models with them

One could also attach external drives (e.g., to supplement the internal SSD with much larger external HDDs).