AL butonu ID si ni jquery ile aldıktan sonra o id değerini içeren (#um_id) inputun içeriğini de almak istiyorum.

 <tr>
    <td><input type="number" class="form-control form-control-sm" id="um_<?php echo $urun['urun_id'];?>" style="max-width: 120px;"></td>

    <td><a class="urunal btn btn-secondary btn-sm"

        id="<?php echo $urun['urun_id'];?>"

        data-auid="<?php echo $auid;?>"

        data-utid="<?php echo $utid;?>"

        data-aiid="<?php echo $aiid;?>"

        data-uf="<?php echo $urun['urun_fiyat'];?>"

        data-nk="0.2"

        data-sid="<?php echo $urun['kullanici_id'];?>"

        data-suid="<?php echo $urun['urun_id'];?>"

        data-aid="<?php echo $kullanicicek['kullanici_id'];?>"

        href="javascript:;">AL</a></td>

    <td><div id="<?php echo $urun['urun_id']; ?>" class="sonuc"></div></td>

</tr>
        $("a.urunal").on("click", function() {

            let nesne = $(this),
            id = nesne.attr("id"),
            auid = nesne.data("auid"),
            utid = nesne.data("utid"),
            aiid = nesne.data("aiid"),
            uf = nesne.data("uf"),
            nk = nesne.data("nk"),
            sid = nesne.data("sid"),
            suid = nesne.data("suid"),
            aid = nesne.data("aid"),
            um = $("#um_"+id).val();

            $.ajax({

                url: "/sistem/urun-al.php",
                data: {
                    id: id,
                    auid: auid,
                    utid: utid,
                    aiid: aiid,
                    uf: uf,
                    nk: nk,
                    sid: sid,
                    suid: suid,
                    aid: aid,
                    um: um
                },
                type: "post",
                beforeSend: function () {
                    $("#"+id+".sonuc").html('<div class="spinner-border text-primary" role="status"><span class="visually-hidden">Loading...</span></div>');
                },
                success: function(cevap) {
                    $("#"+id+".sonuc").html(cevap);
                },
                error: function(cevap) {
                    $("#"+id+".sonuc").html(cevap);
                }


            });

        });

    })

SORUNU BU ŞEKİLDE ÇÖZDÜM BELKİ BİRİSİNE YARDIMCI OLUR 

            let nesne = $(this),
            id = nesne.attr("id"),
            auid = nesne.data("auid"),
            utid = nesne.data("utid"),
            aiid = nesne.data("aiid"),
            uf = nesne.data("uf"),
            nk = nesne.data("nk"),
            sid = nesne.data("sid"),
            suid = nesne.data("suid"),
            aid = nesne.data("aid"),
            um = $("#um_"+nesne.attr("id")).val();