In order to upload large files, you will need to set the following setting in the system.web section of the Web.Config file.

<?xml version="1.0"?>
<configuration>
    <system.web>
        <!-- 1GB in kilobytes, default is 4096 KB or 4MB-->
        <httpRuntime maxRequestLength="1048576" />
    </system.web>
    <system.webServer>
        <security>
            <requestFiltering>
                <!-- 1GB in Bytes, default is 30000000 or approx. 28.6102 MB-->
                <requestLimits maxAllowedContentLength="1073741824" />
            </requestFiltering>
        </security>
    </system.webServer>
</configuration>

For more details refer

ASP.Net IIS: HTTP Error 404.13 The request filtering module is configured to deny a request