SequencePosition

SequencePosition[list,sublist] gives a list of the starting and ending positions at which sublist appears in list.

SequencePosition[list,patt] gives all positions at which sequences matching patt occur in list.

SequencePosition[list,patt,n] includes only the first n occurrences of patt.

Please visit the official Wolfram Language Reference for more details and examples on core symbols.