tehre is information about the size of the firm in the Census/ASEC datasets?

CPS-ASEC has the variable firmsize!. I cannot find a variable like that for Census/ACS using different combination in the search tool: number of employees, employer, work place size etc. Please any hint?

Unfortunately, there is not a comparable variable available from the ACS. This is due to the fact that the ACS does not ask a similar question (ACS codebooks can be found here). You can find all of the work related variables available through IPUMS USA here.