将按钮div放在表格div旁边

body {
  overflow: hidden;
}

.container-table100 {
  width: 100%;
  min-height: 100vh;
  background-color: #f4f5f7;
  display: -webkit-box;
  display: -webkit-flex;
  display: -moz-box;
  display: -ms-flexbox;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-wrap: wrap;
  padding: 33px 30px;
}

.wrap-table100 {
  width: 60%;
}

.table100 {
  background-color: #fff;
}

table {
  width: 100%;
}

th,
td {
  font-weight: unset;
  padding-right: 10px;
  text-align: left;
}

.column1 {
  width: 25%;
  padding-left: 40px;
}

.column2 {
  width: 20%;
}

.column3 {
  width: 20%;
}

.column4 {
  width: 20%;
}

.table100-head th {
  padding-top: 10px;
  padding-bottom: 12px;
}

.table100-body td {
  padding-top: 16px;
  padding-bottom: 16px;
}


/*==================================================================
[ Fix header ]*/

.table100 {
  position: relative;
  padding-top: 60px;
}

.table100-head {
  position: absolute;
  width: 100%;
  top: 0;
  left: 0;
}

.table100-body {
  max-height: 400px;
  overflow: auto;
}

.table100.ver2 .table100-head {
  box-shadow: 0 5px 20px 0px rgba(0, 0, 0, 0.1);
  -moz-box-shadow: 0 5px 20px 0px rgba(0, 0, 0, 0.1);
  -webkit-box-shadow: 0 5px 20px 0px rgba(0, 0, 0, 0.1);
  -o-box-shadow: 0 5px 20px 0px rgba(0, 0, 0, 0.1);
  -ms-box-shadow: 0 5px 20px 0px rgba(0, 0, 0, 0.1);
}

.table100.ver2 th {
  font-family: Lato-Bold;
  font-size: 18px;
  color: #fa4251;
  line-height: 1.4;
  background-color: transparent;
}

.table100.ver2 td {
  font-family: Lato-Regular;
  font-size: 15px;
  color: #808080;
  line-height: 1.4;
}

.table100.ver2 .table100-body tr {
  border-bottom: 1px solid black;
}


/*---------------------------------------------*/

.table100.ver2 {
  border-radius: 10px;
  overflow: hidden;
  box-shadow: 0 0px 40px 0px rgba(0, 0, 0, 0.15);
  -moz-box-shadow: 0 0px 40px 0px rgba(0, 0, 0, 0.15);
  -webkit-box-shadow: 0 0px 40px 0px rgba(0, 0, 0, 0.15);
  -o-box-shadow: 0 0px 40px 0px rgba(0, 0, 0, 0.15);
  -ms-box-shadow: 0 0px 40px 0px rgba(0, 0, 0, 0.15);
}


/* scrollbar body */

.js-pscroll {
  position: relative;
  overflow: scroll;
}

<div class="container-table100">
  <div class="wrap-table100">
    <div class="table100 ver2 m-b-110">
      <div class="table100-head">
        <table>
          <thead>
            <tr class="row100 head">
              <th class="cell100 column1">Name</th>
              <th class="cell100 column2">Date</th>
              <th class="cell100 column3">Type</th>
              <th class="cell100 column4">Status</th>
            </tr>
          </thead>
        </table>
      </div>

      <div class="table100-body js-pscroll">
        <table>
          <tbody>
            <tr class="row100 body" style="border-bottom:1px solid black">
              <tr class="row100 body">
                <td class="cell100 column1">Kavya</td>
                <td class="cell100 column2">01-01-2000</td>
                <td class="cell100 column3">Datamodel</td>
                <td class="cell100 column4">completed</td>
              </tr>

              <tr class="row100 body">
                <td class="cell100 column1">Kavya</td>
                <td class="cell100 column2">01-01-2000</td>
                <td class="cell100 column3">Datamodel</td>
                <td class="cell100 column4">completed</td>
              </tr>
          </tbody>
        </table>
      </div>
    </div>
  </div>
  <div class="dropdown">
    <button type="button" class="dropbtn">dropdown menu</button>
  </div>
</div>