Complex sentence: Initially contemplating a union with the Petites Franciscaines de Marie upon realizing that their respective work and rules were substantially different, Missionaries decided to continue on to Quebec, where they established a youth centre for young women.
Split into simpler sentences: Initially contemplating a union with the Petites Franciscaines de Marie they realized that their respective work and rules were substantially different. The Missionaries decided to continue on to Quebec, where they established a youth centre for young women.