Laptop ram mhz where to see?

Where can I see how much maximum ram mhz go with the laptop?

Should be in the task manager

The device manager or the info page can tell you that. Alternatively you can read out the whole thing via https://www.cpuid.com/softwares/cpu-z.html. The https://ark.intel.com/...Processors then spits out the maximum supported RAM frequency from your CPU.