Using the Federal Reserve's Implicit Price Deflator to Convert to 2020 Dollars
If you want to change the base year of a deflator just divide all values by the value in base year and multiply by 100. For example, if you have deflator with base year 2012:
           2011  2012 2013 ... 2020
Def_2012:    87   100  101      112

Then deflator with base 2020 will be given as:
               2011             2012           2013     ...     2020
Def_2020:    87/112*100   100/112*100      101/112*100      112/112*100

This way you you rescale the implicit deflator to 2020. Afterwards you can just apply the deflator as you would normally do.
Edit:
In order to convert all values to 2020 you can use the following formula:
$$X_{2020} = \frac{X_{t}}{\frac{\text{deflator}_{2020}}{100}}$$
where $X$ is the nominal variable you want to adjust and  subscripts indicate the years with $t$ being an arbitrary year.