upgrade of CPUs

Well, it depends.

First off, do you actually have a need for virtualization, or were you just wanting to fiddle around with it? If you don't really need it, there's not much point in worrying about it.

Second, what is the particular instruction set or capability for the virtualization that is missing from your particular Celeron? For example, one of the earlier sets, VT-x (Intel virtualization), has been standard on Intels' various Celerons since the Core 2-based models (including the earliest single-core versions), while VT-d (I/O MMU virtualization) was introduced with the Skylake-based Celerons. So knowing which particular capability or compatibility option that you need will help determine whether a) your current CPU actually can or cannot run it, & b) what the minimum level of CPU upgrade is that you'd need.

Third, assuming your CPU supported it, do you even have enough resources to work with it? The virtual machine (VM) you'll set up needs more resources than just a CPU to support it, you have to be able to allocate available resources (especially RAM). A PC with only 4 GB of RAM is going to be a very poor VM platform, & even 8 GB of RAM is probably stretching it (unless you're only running a 32-bit VM).

Finally, it's possible that you might be able to upgrade your CPU for one that will provide that virtualization capability, but it's going to depend on your platform. First, if it's a laptop, you might as well just plan on buying a new one; even assuming you lucked out & have a laptop that doesn't have the CPU soldered to the motherboard, the cooling system built into the laptop might not support a more powerful CPU, & it's not only very difficult to take a laptop apart to get to those portions, it's usually even harder to get it put back together correctly. If you have a desktop, it's going to depend on your motherboard. If you know the make (i.e. Gigabyte, MSI, etc.) & model of your motherboard, their websites generally have a list of supported CPUs. Fair warning, some CPU upgrades require that you flash/upgrade the BIOS before installing the new CPU.