If your PC is a desktop, unless your existing PSU has either automatic detection or is capable of being set to a different voltage your best bet would be to replace the PSU with a local unit of the correct rating for the PC. Most laptops have power supplies that are universal but you need to check the unit specification to be certain.
The printer is likely to require replacing or a voltage converter used between it and the mains supply.
For both the speakers and the screen you will need to check the operating specification of the power supply. Details should either be printed or embossed on the case.