I want to know the number of social workers in the US 1950-1970. I have limited quant background so detailed instructions would be appreciated.
Given your time period of interest, you will want to look into using IPUMS USA. IPUMS CPS also has occupation data available, but the earliest samples in which you could find social workers with the given occupation codes would be 1968.
In IPUMS USA these work related variables are available. For what you have described, I would recommend that you look into using the OCC1950 codes, which apply the 1950 Census Bureau occupational classification system to occupational data to enhance comparability across years. As you can see from this list of codes, 079 is the code for social and welfare workers.
If your analysis is purely to find the number of social workers during a given time period, the simplest approach may be to use the Online Data Analysis System (SDA). To be more explicit (based on the information you provided) you could do the following:
choose United States 1850-2016 from “use data from multiple samples” on the IPUMS USA SDA homepage
put occ1950 in row
put year in column
use a selection filter of: occ1950(079), year(1950-1970)
keep the weight as perwt (default)
Otherwise, you can also look into creating a data extract through IPUMS USA. This is a more flexible means of working with the data but would require knowledge of a statistical package such as Stata, SAS, SPSS, etc.