There are two issues here... the first is "what" do you want to do (have access to files) and the second is "how" do you want to solve it?
You've presupposed an answer such as "plug into the PC via USB" ... which isn't an approach I would use.
While you could actually install a web server, it sounds like you really just want remote access to the filesystem. In that case, skip the web server idea.
If you have not done so already, enable the ssh (secure shell) service on your Pi. Older OS versions enabled this by default. Newer Raspbian Stretch OSes disable it by default but it is easy to enable. Just run
sudo raspi-config (this opens a configuration interface). Choose "Interfacing Options" (probably item #5 on the first menu). Next choose "SSH" (probably the 2nd menu option). Select "Yes" as the answer to "Would you like the SSH server to be enabled?". Acknowledge all prompts and it will return you to the main menu. Then tab over to "Finish" to exit rasps-config.
That's it! You're basically done (but probably confused). The "ssh" (secure shell normally used for remote terminal access via a utility such as PuTTY on Windows (any Unix/Linux box would have an "ssh" command line and doesn't need a utility like PuTTY)) also can do secure file transfer protocol (sftp).
Now you need a client on your Windows PC. Filezilla is free and probably the most popular client. I use a commercial (non-free) client. Any client that supports "sftp" will work. Just provide the hostname (or IP address), the username (e.g. the "pi" user or any other user you created) and appropriate password.
The client will give you a file-browser interface showing both your local side (PC) and remote side (the Pi) and you can drag files across at will (just like you can in Windows Explorer, etc.) Some of these utilities support treating the "sftp" connection as if it is a remote disk ... which means you can edit the files as well.
(Note that FileZilla will want to default to "ftp" and not "sftp" but it does support "sftp"). "ftp" is insecure (everything is transferred in-the-clear over networks ... including usernames & passwords) and its rare to find hosts that have the service enabled (or even installed). Make sure you configure your client to use "sftp").
There are slightly more complicated options such as installing a Samba server on the Pi which allows Windows PCs to mount any filesystems that you make available via Samba. See: https://www.raspberrypi.org/documentation/remote-access/samba.md (or just do a web search on installing samba ... you'll find loads of articles and videos).