Set Bootstrap Modal Popup Width using CSS

Hi ramco1917,

Please refer below sample.

HTML

<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap@4.6.1/dist/css/bootstrap.min.css" />
<script src="https://cdn.jsdelivr.net/npm/jquery@3.6.0/dist/jquery.slim.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/popper.js@1.16.1/dist/umd/popper.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/bootstrap@4.6.1/dist/js/bootstrap.bundle.min.js"></script>
<style type="text/css">
    .modal-dialog {
        width: 300px !important;
    }
</style>
<button type="button" class="btn btn-primary" data-toggle="modal" data-target="#myModal">
    Select
</button>
<div class="modal" id="myModal">
    <div class="modal-dialog">
        <div class="modal-content">
            <div class="form-horizontal">
                <div class="modal-body">
                    <div class="row">
                        <div class="col-lg-6 col-md-6 col-sm-12">
                            <div class="form-group">
                                <label>KRA</label>&nbsp;<span style="color: red">*</span>
                                <asp:DropDownList ID="ddlKRA" class="form-control" runat="server" required="true" AutoPostBack="true">
                                    <asp:ListItem Value="">Select KRA</asp:ListItem>
                                </asp:DropDownList>
                            </div>
                        </div>
                        <div class="col-lg-6 col-md-6 col-sm-12">
                            <div class="form-group">
                                <label>Sub KRA</label>&nbsp;<span style="color: red">*</span>
                                <asp:DropDownList ID="ddlSubKRA" class="form-control" runat="server" required="true">
                                    <asp:ListItem Value="">Select Sub KRA</asp:ListItem>
                                </asp:DropDownList>
                            </div>
                        </div>
                    </div>
                </div>
            </div>
        </div>
    </div>
</div>

Screenshot