Your employer will get a new customer, so they will not complain.
The new company will have bought only the hardware, (when buying a new machine with a PLC you will not get the sogtware with it, only a manual)
so with an old machine and the old company is bankrupt nobody has any rights anymore even patents do loose their rights if not paid.
So contact the mill and your new company and try to sort it out.
Do not tell you have everything, just that you can give it a good try as you have experience in the mill. Backups are not very reliable and will have problems when starting up.
The new company will have bought only the hardware, (when buying a new machine with a PLC you will not get the sogtware with it, only a manual)
so with an old machine and the old company is bankrupt nobody has any rights anymore even patents do loose their rights if not paid.
So contact the mill and your new company and try to sort it out.
Do not tell you have everything, just that you can give it a good try as you have experience in the mill. Backups are not very reliable and will have problems when starting up.