How to Merge Audio Files in Audacity

Step1: Launch the app. From the menu bar, select File > Import > Audio (or press Ctrl + Shift + i)

Step2: In the Select One or More Files window, open the folder containing your audio files.
Highlight all the files you want to merge and select “Open.” If your files are in different folders, select File > Import > Audio again.

Step3: Your files will appear in Audacity. You’ll now put these files one after another to then combine them. To do that,
select all files by choosing Select > All from the menu bar or pressing Ctrl+A.

Step4: You’re ready to align your files. To do that, from the app’s menu bar, select Tracks > Align Tracks > Align End to End.

Step5: Your files are now one after another. To now combine these files into a single track, from Audacity’s menu bar,
choose Tracks > Mix > Mix and Render.

Step6: Your files are now merged into one track. You can play this track by clicking the Play button in the toolbar.
To bring this track outside of Audacity as a music file, from the app’s menu bar, select File > Export Audio (or press Ctrl + Shift + E).

Step7: On the How Would You Like to Export window, choose “Export to Computer” since you want to save the resulting file on your PC.

Step8: The Export Audio window will launch. Click the “File Name” field and type a name for the resulting file.
Select “Browse” next to Folder and choose the folder in which you want to save the file.
Click “Format” and select an audio format for your file (choose “MP3 Files” if you aren’t sure, as this format plays on nearly all devices).

Optionally, configure other options. Then, click “Export.”

Credit : https://www.howtogeek.com/how-to-merge-audio-files-on-windows-11/