Pope Eugene IV's encyclical Cantate Domino identifies "flock" with the Catholic Church and clearly excludes "Jews and heretics and schismatics" from membership in the "flock":
The sacrosanct Roman Church…firmly believes, professes, and proclaims that those not living within the Catholic Church, not only pagans, but also Jews and heretics and schismatics cannot become participants in eternal life, but will depart "into everlasting fire which was prepared for the devil and his angels" [Matt. 25:41], unless before the end of life the same have been added to the flock; and that the unity of the ecclesiastical body is so strong that only to those remaining in it are the sacraments of the Church of benefit for salvation, and do fastings, almsgiving, and other functions of piety and exercises of Christian service produce eternal reward, and that no one, whatever almsgiving he has practiced, even if he has shed blood for the name of Christ, can be saved, unless he has remained in the bosom and unity of the Catholic Church.
One is "added to the flock" (i.e., made a member of the Catholic Church) by professing the Catholic Faith and being baptized, as Pope Pius XII wrote in Mystici Corporis Christi §22:
Actually only those are to be included as members of the Church who have been baptized and profess the true faith, and who have not been so unfortunate as to separate themselves from the unity of the Body, or been excluded by legitimate authority for grave faults committed. "For in one spirit" says the Apostle, "were we all baptized into one Body, whether Jews or Gentiles, whether bond or free."[I Cor., XII, 13.] …
Thus, Jews (and anyone else, too) must be baptized and profess the Catholic Faith to be saved.
(cf. John 8:19, where Jesus says to the Pharisees, the precursors of modern-day Talmudic Jews: “You know neither me nor my Father. If you knew me, you would know my Father also.”)