This article will show you how to run ROM files (video game files) on your Nintendo DS. Please note that running ROMs is against Nintendo's terms of service.
Steps

Step 1. Make sure you have everything you need
To run the ROM file on Nintendo DS, you will need:
- DS R4 Card - Used to emulate a Nintendo DS game card. This card can be purchased at electronics stores or specialized computer stores.
- MicroSD card - Used to store ROM files. Find a microSD card with a capacity of at least 1 GB.
- MicroSD Card SD Adapter - Used to connect microSD cards to the SD card slot on your computer. Typically, this adapter is sold with a microSD card. If your computer does not have an SD card slot, buy a microSD to USB adapter.
- The ROM file for the game you want - If you don't have one, search for "[game name] rom nintendo ds". Only download ROMs from trusted websites.

Step 2. Insert the microSD card into the SD adapter
The slot where you want to insert the card is located on the top or side of the adapter.
The microSD card can only be inserted into the adapter in one way. If the card does not insert, do not overdo it - flip the card 180 degrees and try again

Step 3. Plug the adapter into your computer
The SD card slot is located on the side of your laptop or on the chassis of your desktop computer. If there is no SD card slot, use a microSD to USB adapter.
Modern Macs do not have an SD card slot, so you need an SD to USB / C adapter

Step 4. Format the microSD card
You must change the file system of the microSD card to “FAT32” (Windows) or “MSDOS (FAT)” (Mac) in order for it to work on Nintendo DS.

Step 5. Copy the ROM file to the microSD card
To do this, click on the ROM file, press Ctrl + C (Windows) or ⌘ Command + C (Mac), and then follow these steps:
- Windows - Open This PC window, double-click the name of your SD card under Devices and Drives, and then press Ctrl + V.
- Mac - Open a Finder window, click on your SD card name at the bottom left of the window, then press ⌘ Command + V.

Step 6. Remove the microSD card from the computer
For this:
- Windows - Click the flash drive-shaped icon in the lower right corner of the screen (first click the ^ icon), click Eject, and then remove the card and adapter from the computer.
- Mac - Click the Eject icon to the right of the SD card name in the Finder window, and then remove the card and adapter from your computer.

Step 7. Insert the microSD card into the R4 card
The microSD card slot is at the top of the R4 card.

Step 8. Insert the R4 card into the Nintendo DS
Insert this card into the slot where you insert the game cards.

Step 9. Turn on the Nintendo DS
To do this, press the DS power button. Due to the SD card, it may take longer than usual to turn on.

Step 10. Select your card
On the bottom screen of the Nintendo DS, select the "MicroSD" or "SD" option.
If the SD card content is already displayed on the screen, skip this step

Step 11. Select the desired ROM file
Click or select the name of the game on the bottom screen and then wait for the game to load. The game can now be played as usual.