=INDEX([Range of data to be displayed from], MATCH([Identifier to look for], [Where to look for the identifier], [sort option]), [column index optional])
Use the first portion of the INDEX formula to set where the data you want displayed is to come from. Use the MATCH in the second part of the INDEX formula to designate what row to pull the data from. If you have a unique identifier for each row, use that, the set where to look for the unique identifier. The third portion of the INDEX formula is optional. Use this to specify which column to pull the data from if the first portion of the INDEX formula covers multiple columns.
Comments
=INDEX([Range of data to be displayed from], MATCH([Identifier to look for], [Where to look for the identifier], [sort option]), [column index optional])
Use the first portion of the INDEX formula to set where the data you want displayed is to come from. Use the MATCH in the second part of the INDEX formula to designate what row to pull the data from. If you have a unique identifier for each row, use that, the set where to look for the unique identifier. The third portion of the INDEX formula is optional. Use this to specify which column to pull the data from if the first portion of the INDEX formula covers multiple columns.
Here is a link for further explanation...
https://community.smartsheet.com/discussion/auto-filling-cell-based-entry-another-cell