can I use ios 14 on ipad mini

The original iPad Mini cannot be updated beyond iOS 9.3.5 (or 9.3.6 if cellular).

The iPad Mini 2 and 3 cannot be updated beyond iOS 12.4.8.

The iPad Mini 4 can be updated to the current iOS 14.

That would depend upon your iPad mini...

• iPad mini4 or mini5 (current) - iPadOS 14.0.1
• iPad mini2 or mini3 - iOS 12.4.8
• iPad mini1 - iOS 9.3.5 (WiFi Only) or iOS 9.3.6 (WiFi+Cellular)

The tags appended to your post suggest that you have an original first generation iPad mini. Therefore, the answer is no, your iPad mini1 is not compatible with iPadOS 14.