I recorded in Music Creator old cassette tapes and I would like to remove the background noise.
Is there any possibility to improve the recording ?

We digitaze full time vinyl and tapes and also cassette tapes for thousends of clients.
Correct the frequency spectrum with an VST equalizer (we think best is Waves Q10 and Voxengo HarmoniEQ )
The really and "only" way to remove background noise from tapes is iZotope RX with the VST plugin Spectral De-Noise. Its in the Standard version from iZotope RX.
https://www.izotope.com/en/products/repair-and-edit/rx/rx-standard.html

Noise with -45dB goes down to -70dB. If you want to have it absolut silent, take a gate after the de-noiser, starting at -60dB.
Then you "learn" the plugin before a record starts to the noise, or between two records where you have 2 seconds of noise. Its called a noise-print. Then apply this de-noiser with this learned noise-settings (noise-print) to the whole tape record. Make a new "noise-print" for every cassette.
 
 

If you just want to test something for free, then Audacity is something worth trying. It has a "noise-learn" function.
It's not as capable as Izotope, but who knows....

Don't you still have the original files ( BUN< CWP>WORK? ) for MC?  seems that would be a simple matter of loading the songs and export? 
If not look to using a Wave Editor, Sound Forge has good tools I got my copy free with a Sony Turntable. It works for LP's.  but the best is said to be isotope. 

I think the audacity ones work welll. Although have considered Waves NS1. Izotope RX is going to give you the best all round results for the money. Algorithmix, Sony Oxford (Sonnox) Restoration and Cedar tools exist (I believe that was used to clean up the original master tapes for The Beatles Love Album). Very expensive though. Well the fact you have to request a demo says it all.