The base package of Apache Commons Lang 3 is not org.apache.commons.lang anymore.
Provided that the error occurs in your own code, you have to replace it with the org.apache.commons.lang3 package .
If it occurs in external libraries, either upgrade them to a version that uses Lang 3 (if it is possible), or you may have to also keep your older commons lang among the dependencies (as explained in the answer by Karol, the distinct packages will prevent possible conflicts anyway).
e.g :
org.apache.commons.lang.StringUtils in Lang 2.6
vs
org.apache.commons.lang3.StringUtils in Lang 3
commons-lang3 is using org.apache.commons.lang3 base package to avoid conflicts with previous versions of commons-lang. This allows both 2.X and 3.X to be used at the same time.
To update to 3.X uou have to change the import in your code e.g. use
import org.apache.commons.lang3.StringUtils;