Let me help you upload your old bulk data to Firebase

1. Export the Excel file as CSV

2. Use this tool to convert this CSV to JSON

3. Use a text editor Find-and-Replace to change { to "x": {. Also remove the [] in the beginning and ending.

4. Use this Linux command to change each of the x to incemental numbers

awk 'BEGIN { cntr = 0 } /"x":/ { cntr++ ; print "\""cntr"\":" } !/header/ { print $0 }' codebeautify.json > output.json

(Remember this code doesn't do the exact thing for us, so one more step)

5. "x": is not removed, so to remove it use text editor Find-and-Replace to change "x": to blank.

6. Last step, but important - convert the encoding of the file to strictly UTF-8, nothing else is accepted.

Done! Goto Firebase Database Console and upload the output.json using Import JSON.

Recommended to use Visual Studio Code for the purpose (especially Step 6).