This tells you that you have approx 2.7TB of library on Sooloos.

The export will be not less than this.

Take Carl’s point about artwork and estimate that 122,000 tracks will embed a cover art of whatever size your typical artwork is.

That should give you a ball park figure.

Take from the stats thread I linked above and multiply your 9000 albums by an average of maybe 350mb or 400mb per album

This would suggest between 3TB and 4TB as well.

Does this match what you found so far?

Rgds,
Nick