$ImportFormats
gives a list of import formats currently supported in your Wolfram Language session.
Examples
open allclose allProperties & Relations (1)
$ExportFormats lists formats supported by Export:
Wolfram Research (1999), $ImportFormats, Wolfram Language function, https://reference.wolfram.com/language/ref/$ImportFormats.html.
Text
Wolfram Research (1999), $ImportFormats, Wolfram Language function, https://reference.wolfram.com/language/ref/$ImportFormats.html.
CMS
Wolfram Language. 1999. "$ImportFormats." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/$ImportFormats.html.
APA
Wolfram Language. (1999). $ImportFormats. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/$ImportFormats.html