Inserting values into a column when Table1 column A value matches Table 2 Column B Value
Taking a guess that Vinny wishes to update the PurchaseInfo table, and that SupplierInfo is same as ImportData

UPDATE PurchaseInfo 
SET [Supplier Contact Name] = S.[Supplier Contact Name]
FROM ImportData I JOIN PurchaseInfo PI ON PI.[Supplier Name] = I.SupplierName