pick up his cross and follow after me

"carry his cross and follow me." The cross represents suffering and death. Taking up the cross represents being willing to suffer and die. Alternate translation: "obey me even to the point of suffering and dying" (See: rc://en/ta/man/translate/figs-metonymy and rc://en/ta/man/translate/figs-metaphor)

pick up

"take up" or "pick up and carry"