Yes, but natively is hard. You can use Wine to run the Windows tools, or use 3DShell (a homebrew for 3DS similar to GodMode9). Alternatively, download Ultimate 3DS Converter for Mac (community maintained, but less stable than GodMode9).
Before converting, you need:
A .3ds file is a raw, sector-by-sector dump of a Nintendo 3DS game cartridge. Think of it as a digital clone of the physical card. .3ds to .cia converter