In Nexis Uni, look for the "Guided Search" box and select the "Cases" button. From there, you can choose either Federal or State cases and type in your search terms. You can also choose to search within a particular date range.
You can also find many legal cases and opinions in Google Scholar. At the top left of the page are three lines next to the GoogleScholar logo. Click that and then choose "Case Law" instead of "Articles." Depending on your search, you may be able to further limit your results to federal or state cases (in the case of the sample search, you will have the option to display results from Pennsylvania courts).