Can I upload photos on a SD card to my MacBook Air?

Sure, once you plug it in use Image Capture if it did not already launch, or use file->import directly from Photos.

You would need an appropriate SD card reader, of course.

Potentially, yes ... but, without a lot more details from you, there is no way we can tell you for sure.

I bought this from Amazon for $5

SD Card Reader, SmartQ Dual Connector

USB 2.0/USB-C Memory Card Reader Adapter,

Compatible with SD/Micro SD/SDHC/SDXC/MMC [Card not Included],

Suitable for MacBook Pro/Air, iPad Pro.

They're all pretty much the same. I saw one that said USB 3 for $7-- might be faster, depending on the SD card.