Try to find a site HTTPS requests.
I use chrome, this small point lock (if IE is also possible on the page, right, Properties, Advanced, certificate)
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See the figure below, click "Copy to file"
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The exported certificate labeled .store
Packaged with this command: keytool -import -alias "my.store" -file "E: \ my.store.cer" -keystore my.store
The certificate into the jmeter
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