Scanning documents with your own printer / scanner
If you have a flatbed scanner or scanner-printer attached to your computer or laptop, then you can use this device to scan your documents. It is not particulary important which document format the scanner gives you - PDF or JPEG image are the most common and can be viewed on almost any device.
For Turnitin assignments you will often need to either insert a scanned image into your written assignment or, in the case of PDF, join the scanned document to your other written document(s). More information is available from Joining Different Files into one Document.
Some documents are fine to be photographed with a mobile device and then emailed or used as an image in another document.
Microsoft Office Lens
Microsoft Office Lens is an app (iPhone/iPad | Android) that allows you to use your mobile device as a portable scanner. It is completely free, very easy to use and can be linked to your university OneDrive account by simply logging into it. It will create jpeg image / PDF / Word file (you can choose) from any scanned paper document.
Office Lens intro video
Direct link to video on YouTube: https://youtu.be/Z0iZ8l4b3k8